Bias Ply Tire Sizes

Motorcycle Tire Guide 101 and FAQ

May 18, 2016 – 05:57 am

Welcome to Tire School!

We're going to have a crash course (figuratively speaking!) on tires. This is literally where the rubber meets the road.

At RevZilla, we deal with a vast spectrum of customers, from sponsored racers on rockets to green rookies on Ninja 250s, to someone pushing hundreds of miles daily on a Harley bagger — and that’s just the street riders! One thing they all have in common is that tires are critical components.

Like with most of the products we sell, making a good decision when choosing tires is a matter of understanding how you ride, being honest about your intents and abilities, and most importantly, being safe. Let’s start with a quick run-down of tire terminology.

Basic tire construction terms

Tread: This is the part you see that hits the road, and the part most people think about. In general, smoother tread works better on smooth, dry surfaces, and “chunkier” tires work better off-road. Some street tread patterns are designed to do better in the wet and off-road tires come in a wide variety for different surfaces, from hard-packed dirt to sand.

Bead: This is the part of the tire that mates to the wheel. It is typically steel wire covered heavily in rubber. The bead has a snug fit to the wheel to prevent the wheel from slipping rotationally in the tire.

Carcass: In simple terms, this is the “body” of the tire under the tread. Motorcycle tires are typically bias-ply or radial, which refers to how the tire is constructed. Radial tires have reinforcing belts (which are almost always steel) running from bead to bead across the tread of the tire. Bias-ply tires have belts which are typically cords made of fiber, such as polyester, aramid, or fiberglass, that run from bead to bead at an angle of 30 to 40 degrees or so. (That’s the bias!)

Sidewall: The area of the tire that bridges the tread and bead. A small part of the tire, it is vitally important. It gives the tire much of its handling and load transfer characteristics. This is the part of the tire we’re talking about when we reference height, profile, or aspect ratio. Typically, a shorter sidewall yields a stiffer sidewall, which tends to flex less. To a rider, this means better handling and turning, worse bump absorption, and more difficult mounting. This section greatly contributes to the tire’s role in the suspension. That’s right — the tire is a suspension component!

Cracking the code

How do you know the important stuff about a tire? Like, what’s inside it and what size it is? It's easy. By law, this information is written on the tire sidewall.

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